Lithographic Crystallinity Regulation in Additive Fabrication of Thermoplastics (CRAFT)

For semicrystalline polyolefin thermoplastics, the balance between interconnected ordered crystalline and disordered amorphous regions is paramount to their performance and processability. However, contemporary manufacturing strategies, from injection molding to 3D printing, result in monolithic objects, unable to spatially encode crystallinity. We present the discovery of a light-based approach for fabricating mechanically robust polyolefin thermoplastics with microscopic control over crystallinity in 3D space. We unveil that light dosage governs polymer stereochemistry, giving access to a continuum of materials, from strong, rigid plastics, like HDPE, to more extensible materials akin to LDPE, all at the flick of a switch. Applying this finding to lithographic grayscale 3D-printing in a process we term CRAFT for Crystallinity Regulation in Additive Fabrication of Thermoplastics results in rapid multimaterial fabrication of high-fidelity objects.